He has, effectively, received a one match international ban for a gratuitous stamp that could have broken a fellow player's ankle.
The original disciplinary panel attempted to ensure that Healy missed at least 2 Six Nations matches by extending Healy's 3 week ban over 4 weeks but their attempt to manipulate the regulations was in itself a breach of their powers - hence Healy's availability to play France next up.
It strikes me that there is a straightforward solution. If a chargeable offence is committed playing international rugby, then any ban should apply to only international rugby - 3 international matches would have, rightly, ruled Healy out the rest of the Six Nations but would have allowed him to play for his club/province (who arguably should not suffer from offences committed when not on their watch). Likewise any ban suffered playing club rugby should not necessarily apply to international rugby.